Organic phosphites are well-known and are commonly used as secondary antioxidants in polymer compositions including, for example, polyolefins, polyvinyl chloride, and elastomers. Examples of such phosphites are disclosed in H. Zweifel (Ed) Plastics Additives Handbook, 5th edition, Hanser Publishers, Munich 2000. Phosphite stabilizers, both liquid and solid, are known in the art.
Solid organic phosphite stabilizers are widely used as secondary antioxidants in polymer compositions. One commercially available antioxidant is tris(2,4-di-t-butylphenyl) phosphite, shown below, a solid antioxidant commonly known as Alkanox™ 240, Irgafos™ 168 and Doverphos™ S-480. U.S. Pat. No. 5,254,709, the entirety of which is incorporated herein by reference, describes the synthesis of tris(2,4-di-t-butylphenyl)phosphite by reacting 2,4-di-t-butyl phenol with phosphorus trichloride in the presence of catalyst. The isolated phosphite is described as a white crystalline solid having a melting between 180-185° C.

Tris(2,4-di-t-butylphenyl)phosphite has been demonstrated to effectively reduce peroxide induced oxidative degradation for many polymers including polyolefins, polycarbonates, ABS and polyesters. The trialkylaryl phosphite has low volatility that allows for its use at high temperatures commonly required for processing thermoplastic polymers. Owing to its solid form and concomitant processing limitations, however, tris(2,4-di-t-butylphenyl)phosphite is not well-suited for the stabilization of all polymers and has been demonstrated to plate out during processing of some plastics, in particular low melting point plastics, and forming deposits on processing machinery surfaces.
Liquid phosphite compositions are also well known and do not possess the handling problems associated with solid phosphite compounds. In addition, liquid phosphite compositions generally exhibit better processability than solid phosphite compositions for polymers that process at low temperatures. Tris(p-nonylphenyl)phosphite (TNPP), for example, is one alkylaryl phosphite that is a stable liquid at ambient conditions.
TNPP is a versatile phosphite stabilizer that is useful in stabilizing a large number of polymers such as HDPE, LLDPE, SBR, ABS, PVC and others. There is, however, a need to replace TNPP due to the alleged estrogenicity of nonylphenol, which is commonly used in the synthesis of TNPP.
Many commercially available alkylaryl phosphites share a common alkyl group. U.S. Pat. No. 5,254,709, for example, the entirety of which is incorporated herein by reference, describes the synthesis of tris(2,4-di-t-butylphenyl)phosphite by reacting a 2,4-di-t-butyl phenol with phosphorus trichloride in the presence of catalyst according to the following reaction:

U.S. Pat. No. 7,468,410 describes a mixture of phosphites including a tri(4-sec-butylphenyl)phosphite and a tri(2-sec-butylphenyl)phosphite. Each of these phosphites is a liquid when isolated, and the combination is a liquid.
U.S. Pat. No. 5,254,709 describes various secondary antioxidants including a solid phosphite made from 2:1 molar ratio of 2,4-di-t-amyl phenol and 2,4-di-t-butyl phenol, and a liquid phosphite made from 2-t-butyl-4-nonyl phenol.
The need remains for novel, safe and effective phosphite stabilizers that can effectively stabilize polymer resins and compositions against heat and light degradation and that are liquid at ambient conditions.